Method and apparatus for etching a deep trench

Abstract

A method for plasma etching a trench in a semiconductor substrate using a plurality of processing cycles comprising plasma etch and deposition periods, wherein a substrate bias power is pulsed during the etch periods.

What is claimed is:  
     
         1 . A method for plasma etching a trench in a semiconductor substrate to reduce scalloping of the trench, comprising: 
 applying a plurality of processing cycles to the substrate, where each cycle comprises a plasma etch period and a plasma deposition period; and    pulsing a substrate bias power during the plasma etch period.    
     
     
         2 . The method of  claim 1  wherein the trench has a width between 1 to 20 μm and an aspect ratio of about 5 to 50.  
     
     
         3 . The method of  claim 1  wherein the trench has scallops having a peak-to-valley size that is less than 100 nm.  
     
     
         4 . The method of  claim 1  wherein the plasma etch period has a duration between 1 and 40 seconds.  
     
     
         5 . The method of  claim 1  wherein the plasma etch period comprises a plasma etch process that uses an etchant gas comprising SF 6 .  
     
     
         6 . The method of  claim 1  wherein the plasma deposition period has a duration between 1 and 20 seconds.  
     
     
         7 . The method of  claim 1  wherein the plasma deposition period comprises a plasma process that uses at least one of a fluorocarbon gas and a hydrofluorocarbon gas.  
     
     
         8 . The method of  claim 7  wherein the fluorocarbon gas comprises C 4 F 8 .  
     
     
         9 . The method of  claim 7  wherein the hydrofluorocarbon gas comprises CHF 3 .  
     
     
         10 . The method of  claim 1  wherein the pulsing step further comprises: 
 applying the substrate bias power between 1 and 30 milliseconds at a duty cycle of between 10 and 90%.  
 
     
     
         11 . The method of  claim 1  wherein the pulsing step further comprises: 
 applying the substrate bias power for about 6 milliseconds at a duty cycle of about 33%.  
 
     
     
         12 . The method of  claim 1  wherein a source power is continuously applied to the plasma while the substrate bias power is pulsed.  
     
     
         13 . The method of  claim 12  wherein the source power has a frequency of about 12.56 MHz and the substrate bias power has a frequency of about 400 KHz.  
     
     
         14 . A computer-readable medium including software that, when executed by a processor, performs a method that causes an etch reactor to etch a trench in a semiconductor substrate to reduce scalloping of the trench, comprising: 
 applying a plurality of processing cycles to the substrate, where each cycle comprises a plasma etch period and a plasma deposition period; and    pulsing a substrate bias power during the plasma etch period.    
     
     
         15 . The computer-readable medium of  claim 14  wherein the trench has a width between 1 to 20 μm and an aspect ratio of about 5 to 50.  
     
     
         16 . The computer readable medium of  claim 14  wherein the trench has scallops having a peak-to-valley size that is less than 100 nm.  
     
     
         17 . The computer-readable medium of  claim 14  wherein the plasma etch period has a duration between 1 and 40 seconds.  
     
     
         18 . The computer-readable medium of  claim 14  wherein the plasma etch period comprises a plasma etch process that uses an etchant gas comprising SF 6 .  
     
     
         19 . The computer-readable medium of  claim 14  wherein the plasma deposition period has a duration between 1 and 20 seconds.  
     
     
         20 . The computer-readable medium of  claim 14  wherein the plasma deposition period comprises a plasma process that uses at least one of a fluorocarbon gas and a hydrofluorocarbon gas.  
     
     
         21 . The computer-readable medium of  claim 20  wherein the fluorocarbon gas comprises C 4 F 8 .  
     
     
         22 . The computer-readable medium of  claim 20  wherein the hydrofluorocarbon gas comprises CHF 3 .  
     
     
         23 . The computer-readable medium of  claim 14  wherein the pulsing step further comprises: 
 applying the substrate bias power between 1 and 30 milliseconds at a duty cycle of between 10 and 90%.  
 
     
     
         24 . The computer-readable medium of  claim 14  wherein the pulsing step further comprises: 
 applying the substrate bias power for about 6 milliseconds at a duty cycle of about 33%.  
 
     
     
         25 . The method of  claim 14  wherein a source power is continuously applied to the plasma while the substrate bias power is pulsed.  
     
     
         26 . The method of  claim 14  wherein the source power has a frequency of about 12.56 MHz and the substrate bias power has a frequency of about 400 KHz.